Hydrophobic porous membranes and process for the manufacture thereof

Abstract

Disclosed is a hydrophobic porous membrane with a polymer having fluorinated alkyl side chains held in physical contact with the surface of a polyolefin porous membrane in which the fluorinated alkyl side chains of the polymer are crystallized, as well as its manufacturing process. Also disclosed is a hydrophobic porous membrane with a fluorinated crosslinked polymer from a fluorinated monomer with a fluorinated alkyl side chain and a crosslinking monomer held in physical contact with the surface of a polyolefin porous membrane, in which the fluorinated alkyl side chains of the fluorinated crosslinked polymer are crystallized, as well as its manufacturing process. These porous membranes use polyolefin porous membranes having a higher mechanical strength and lower costs than the fluorinated polymer porous membranes and still provide superior hydrophobicity over polytetrafluoroethylene type membranes.

What is claimed is: 
     
       1. A hydrophobic porous membrane comprising a polyolefin porous membrane and a polymer having a fluorinated alkyl side chains, wherein the polymer is held in physical contact with the surface of said polyolefin porous membrane and the fluoroalkyl side chains of said polymer are crystallized. 
     
     
       2. A hydrophobic porous membrane as set forth in claim 1 in which the polymer having fluorinated alkyl side chains is a polymer of a fluorinated alkyl methacrylate or a fluorinated alkyl acrylate. 
     
     
       3. A hydrophobic porous membrane as set forth in claim 1 in which the polymer having fluorinated alkyl side chains is a polymer of a fluorinated alkyl methacrylate or a fluorinated alkyl acrylate having at least 7, but not more than 15 carbon atoms in the ester moiety thereof. 
     
     
       4. A hydrophobic porous membrane as set forth in claim 1 in which the polymer having fluorinated alkyl side chains is a polymer of a perfluoroalkylethyl methacrylate or perfluoroalkylethyl acrylate having at least 7, but not more than 15 carbon atoms in the ester moiety thereof. 
     
     
       5. A hydrophobic porous membrane as set forth in claim 1 in which the polyolefin porous membrane is a polyethylene or polypropylene porous membrane. 
     
     
       6. A hydrophobic porous membrane as set forth in claim 1 in which the polyolefin porous membrane is a polyethylene hollow fiber membrane or polypropylene hollow fiber membrane. 
     
     
       7. A hydrophobic porous membrane as set forth in claim 1 in which the polyolefin porous membrane is a polyolefin flat membrane. 
     
     
       8. A hydrophobic porous membrane as set forth in claim 1 in which the polyolefin porous membrane is a polyolefin woven membrane. 
     
     
       9. A hydrophobic porous membrane comprising a polyolefin porous membrane and a fluorinated crosslinked polymer from a fluorinated monomer having a fluorinated alkyl side chain and a crosslinking monomer, wherein the polymer is held in physical contact with the surface of said polyolefin porous membrane and the fluorinated alkyl side chains of said fluorinated crosslinked polymer are crystallized. 
     
     
       10. A hydrophobic porous membrane as set forth in claim 7 in which the fluorinated monomer having a fluorinated alkyl side chain is a fluorinated alkyl methacrylate or fluorinated alkyl acrylate. 
     
     
       11. A hydrophobic porous membrane as set forth in claim 7 in which the fluorinated monomer having a fluorinated alkyl side chain is a fluorinated alkyl methacrylate or fluorinated alkyl acrylate having at least 7, but not more than 15, carbon atoms in the ester moiety thereof. 
     
     
       12. A hydrophobic porous membrane as set forth in claim 7 in which the fluorinated monomer having a fluorinated alkyl side chain is a perfluoroalkylethyl methacrylate or perfluoroalkylethyl acrylate having at least 7, but not more than 15, carbon atoms in the ester moiety thereof. 
     
     
       13. A hydrophobic porous membrane as set forth in claim 7 in which the crosslinking monomer is a polyfunctional methacrylate or polyfunctional acrylate. 
     
     
       14. A hydrophobic porous membrane as set forth in claim 7 in which the polyolefin porous membrane is a polyethylene or propylenc porous membrane. 
     
     
       15. A hydrophobic porous membrane as set forth in claim 7 in which the polyolefin porous membrane is a polyethylene hollow fiber membrane or a polypropylene hollow fiber membrane. 
     
     
       16. A hydrophobic porous membrane as set forth in claim 7 in which the polyolefin porous membrane is a polyolefin flat membrane. 
     
     
       17. A hydrophobic porous membrane as set forth in claim 7 in which the polyolefin porous membrane is a polyolefin wovcn membrane. 
     
     
       18. A process for the manufacture of a hydrophobic porous membrane, comprising the steps of holding a polymer having fluorinated alkyl side chains in physical contact with the surface of a polyolefin porous membrane and heat treating, thereby crystallizing said fluorinated alkyl side chains. 
     
     
       19. A process for the manufacture of a hydrophobic porous membrane, comprising the steps of adhering a monomer having a fluorinated alkyl side chain to the surface of a polyolefin porous membrane, polymerizing in situ to hold the polymer having fluorinated alkyl side chains in physical contact with the surface of the polyolefin porous membrane, and heat treating, thereby crystallizing said fluorinated alkyl side chains. 
     
     
       20. A process for the manufacture of a hydrophobic porous membrane, comprising the steps holding a fluorinated crosslinked polymer from a fluorinated monomer having a fluorinated alkyl side chain and a crosslinking monomer in physical contact with the surface of a polyolefin porous membrane, and heat treating, thereby crystallizing said fluorinated alkyl side chains. 
     
     
       21. A process for the manufacture of a hydrophobic porous membrane, comprising the steps adhering a fluorinated monomer having a fluorinated alkyl side chain and a crosslinking monomer to the surface of a polyolefin porous membrane, polymerizing in situ to hold the fluorinated crosslinked polymer composed of the fluorinated monomer having a fluorinated alkyl side chain and the crosslinking monomer in physical contact with the surface of the polyolefin porous membrane, and heat treating, thereby crystallizing said fluorinated alkyl side chains.